Known resid hydrotreating systems produce carbonaceous solids which foul separators, stills, and other downstream processing units. Therefore, it is both desirable and advantageous to remove these solids from the hydrotreated effluent as early as possible in the refining process and at the first convenient opportunity, especially before the temperature of the effluent is reduced significantly.
The prior art discloses distilling light and heavy vacuum gas oil from the effluent prior to deasphalting. While this distillation tends to minimize the load on the solvent extraction unit, the practice also requires a vacuum tower. Also, since certain streams from a deasphalter ("SEU") are subsequently commingled with vacuum gas oils, the distillation process steps are somewhat redundant. Further, the hydrotreated effluent is cooled prior to fractionation which contributes to the downstream fouling.